The present invention relates to improvements made to devices for blow molding or stretch-blow molding containers, especially bottles, from thermoplastic preforms. The device includes a bill-fold type mold having two half-shells joined to each other by a mutual pivoting pin, coinciding with respective edges of the two half-shells, and actuation means associated with the two half-shells in order to pivot the latter with respect to each other in the mold-closing direction or in the mold-opening direction, as well as to container manufacturing plants which make use of such a molding device.
Document FR-A-2,646,802 shows, in its FIG. 4, one arrangement of a bill-fold mold as mentioned above, in which the mold is closed and opened by a reciprocating rotational motion of a driving arm. The said reciprocating rotational motion is described and shown as being conferred by a driveshaft perpendicular to said arm to which it is fastened by fitting onto a square, but no information is provided with regard to the manner in which the driveshaft itself is set into motion.
The object of the present invention is essentially to provide a simple technical solution which can be used to set a mold in motion, such as the one in FIG. 4 of the aforementioned document, and also to provide, because of the simplicity of said means, a complete manufacturing plant constructed around such a single-mold molding device, the half-shells of which can pivot about a fixed pin, which has a simple and reliable design and is capable of maintaining synchronous operation of all its component parts.
Such a single-mold device and fixed pivoting pin are already known from document EP 0,456,866. However, this document does not tackle the problem of synchronizing the opening and closing of the mold with the operation of the other elements of the machine.